Better. I’ll attend to your case, young man, after school.
Bad. It is hard for me to write while tending the baby.
Better. It is hard for me to write while taking care of the baby.
than, till, until. Not synonyms for when after hardly or scarcely.
Wrong. Hardly had he fired than the burglar fell.
Right. Hardly had he fired when the burglar fell.
Wrong. She had scarcely spoken until we arrived.
Right. She had scarcely spoken when we arrived.
United States. Should be preceded by the when used as a noun.